YOU SAID:

your sister is more stupider

INTO JAPANESE

あなたの妹はより stupider です。

BACK INTO ENGLISH

Is your sister is stupider.

INTO JAPANESE

あなたの妹が stupider です。

BACK INTO ENGLISH

Your sister is stupider.

INTO JAPANESE

あなたの妹は stupider です。

BACK INTO ENGLISH

Your sister is stupider.